(594b) Dynamics and mechanism of self-assembly and formation of functional silk-based structures from silk fibroin protein polymers

Min, Y., University of Akron

Bombyx mori silk fibroin (SF) protein polymers are versatile biomaterial matrices that have been widely used for a variety of applications ranging from biomedical materials to electronic and photonic devices. Much is known about the processing types and conditions for producing silk-based structures (e.g. fibers, microcapsules, films, hydrogels or sponges) from SF protein polymers, but much less about the mechanism and dynamics of formation of such structures. In particular, there is a limited amount of information on how such structures self-assemble from their constituent molecules (i.e. SF protein polymers) and how the SF protein polymers interact with each other and behave in solution under nanoconfined environments. This presentation summarizes our recent studies and findings in this context. We have studied how SF protein polymers aggregate or bundle to form continuous fibers when they are pressed together and/or sheared each other using the Surface Forces Apparatus (SFA) as well as various mechanical characterization and microscopy imaging techniques. We find that aggregation of these SF protein polymers occur once a critical local pressure and/or sliding speed are reached. The magnitude of these critical values are significantly affected by the processing parameters such as the concentration of SF protein polymers and number of compression-decompression cycles (i.e. history of the sample). The presentation also involves the discussion and comparison of the complex dynamics of force profiles for SF protein polymers with other protein-based phenomena. We anticipate that study of dynamics and self-assembly SF protein polymers is not only of fundamental research value but also of practical significance, since it facilitates the fabrication of nanoscale SF based materials (e.g. fibers and thin films) with superior properties than traditional bulk materials.